The present invention relates to a method for the introduction of a liquid, such as a liquid fuel, into a receptacle such as a steelmaking converter, especially into a converter in which refining is achieved by means of industrially pure oxygen blown into the converter through its bottom or its lateral wall.
The injection of industrially pure oxygen through the bottom or lateral wall of a converter generally involves the use of at least one tuyere comprising two coaxial conduits, with the central conduit being used to introduce oxygen and the peripheral conduit to allow the passage of a shielding fluid. In the event of the tuyere or tuyeres being housed in the lateral wall, they are located below the normal upper level of the metal when the converter is in the vertical position.
When a liquid shielding fluid is used, it is most usually a hydrocarbon, the vaporization and endothermic decomposition of which at the outlet of the peripheral conduit, inside of the converter, are particularly advantageous from the point of view of protecting the bottom or lateral wall from attack by the oxygen. More generally, this shielding liquid is injected into the converter in such a way that its pressure at the tuyers aperture on the inside of the converter is at least 1 kg/cm.sup.2.
With this type of injection, certain particularly unpleasant disadvantages may manifest themselves during sudden and unforeseen variations in the pressure of the liquid supplied by the peripheral conduit.
Such a variation, involving a rapid drop in pressure, may be caused by the following circumstances. At the outlet apertures of the peripheral conduits inside the converter it is possible, in certain circumstances, for metallic deposits to form and partially block the apertures. These then allow the passage of only part of the liquid which is to be introduced and, in order to maintain the effective flow of the liquid unchanged or to keep it at a minimum value, it is necessary to increase its supply pressure. It should be remembered that in the present case, the rate of flow of the liquid shielding fluid can hardly be modified at all generally speaking, because if it is too low, the protection of the converter refractories is incomplete and if it is too high, part of the fluid is not decomposed and ends up leaving the converter unused or unburnt.
It may be that the metallic deposits to which reference is made above suddenly become detached from the place where they were fixed and this clearly and rapidly facilitates the passage of the shielding liquid through the peripheral conduits of the tuyeres; since, at this moment, the injection pressure of the liquid is greater than that needed to ensure the desired rate of flow in the absence of any back pressure or parasitic pressure loss (for example resulting from the presence of such deposits), the rate of flow of the shielding fluid suddenly increases significantly, and the drawbacks referred to above manifest themselves. In extreme cases, the surplus fluid is discharged from the converter, polluting either the neighboring areas or the external wall of the converter. It has even been shown that this surplus liquid may progressively impregnate the refractories of the converter lining until it passes through them completely and oozes out of them. In such cases, there is an obvious need to reduce as quickly as possible the pressure at which the liquid is delivered by its supply pump, but this can, in most cases, only be achieved after a certain delay and thus it is not possible to avoid the disadvantages which have been referred to.
Similar difficulties may manifest themselves when it is desired to increase the pressure at which the liquid is supplied, as an increase in this pressure leads the pressure drop and back pressure being unaltered) to a corresponding increase in the rate of flow, this being undesirable.
What is desired is a method allowing a simple control of the introduction of liquid, such as a fuel, into a receptacle, such as a converter (beneath the level of the molten metal), through at least one injection conduit; this conduit may for example, be the peripheral conduit of a blowing tuyere having two coaxial conduits, housed in the bottom or lateral wall of a converter, with the central conduit serving to blow in an oxidizing gas.